Horizontal stabilizer trim actuator systems and methods

ABSTRACT

Systems and methods are provided for a hydraulic stabilizer trim actuator (HSTA). The HSTA may operate one or more movable control surfaces. The HSTA operate responsive to commands issued by the pilot and/or by a controller and may include hydraulic architecture that minimizes the probability of an un-commanded movement or movement in the opposite direction of such commands.

TECHNICAL FIELD

The disclosure relates generally to aircraft control surface systems andmore specifically to Horizontal Stabilizer Trim Actuator (HSTA) systemsused to control horizontal control surfaces.

BACKGROUND

Aircraft often include one or more control surfaces such as, forexample, one or more horizontal stabilizers. The horizontal stabilizermay be located, for example, at the rear of the aircraft and may includeelevator control surfaces that are attached that may be used to changethe pitch of the aircraft. A Horizontal Stabilizer Trim Actuator (HSTA)may be used to move the horizontal control surface. The HSTA may be, forexample, a hydraulic system that may actuate the horizontal controlsurface responsive to commands issued by a controller or pilot of theaircraft.

In certain examples, the horizontal control surface may be moved toalleviate load on the elevator control surfaces. In such examples,un-commanded or unintended movement of the horizontal stabilizer may notbe desirable. As such, a HSTA designed to prevent such un-commanded orunintended movement is desirable.

SUMMARY

Systems and methods are disclosed herein for a hydraulic stabilizer trimactuator. In certain examples, a system may be disclosed and may includea hydraulic inlet configured to receive pressurized hydraulic fluid, afirst hydraulic path fluidically connected to the hydraulic inlet, asecond hydraulic path, a hydraulic shutoff apparatus fluidicallyconnected to the first hydraulic path and the second hydraulic path andconfigured to be switched between a plurality of hydraulic positionswherein at least one of the hydraulic positions allows for thepressurized hydraulic fluid to flow from the first hydraulic paththrough the hydraulic shutoff apparatus to the second hydraulic path, adirectional and rate control apparatus, a third hydraulic pathfluidically connected to the directional and rate control apparatus, anda hydraulic motor fluidically connected to the directional and ratecontrol apparatus via the third hydraulic path. The directional and ratecontrol apparatus may be configured to be switched between a pluralityof directional control positions where at least one of the directionalcontrol positions allows for the pressurized hydraulic fluid to flowfrom the second hydraulic path through the directional and rate controlapparatus to the hydraulic motor. The hydraulic motor may be configuredto turn an output shaft to actuate a control surface of a vehicleresponsive to receiving the pressurized hydraulic fluid from thedirectional and rate control apparatus and configured to be lockedresponsive to not receiving the pressurized hydraulic fluid from thedirectional and rate control apparatus.

In certain other examples, a method may be disclosed and may includereceiving pressurized hydraulic fluid, flowing the pressurized hydraulicfluid into a hydraulic shutoff apparatus, switching, responsive to theflow of the pressurized hydraulic fluid into the hydraulic shutoffapparatus, the hydraulic shutoff apparatus to a first hydraulicposition, flowing the pressurized hydraulic fluid into a directional andrate control apparatus, switching, responsive to the flow of thepressurized hydraulic fluid into the directional and rate controlapparatus, a directional control valve of the directional and ratecontrol apparatus to a first directional control position, monitoringthe position of the directional control valve, actuating, responsive tothe flow of the pressurized hydraulic fluid into the hydraulic motor,the hydraulic motor, turning an output shaft of the hydraulic motor, andactuating a control surface.

The scope of the invention is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of the disclosure will be afforded to those skilled in theart, as well as a realization of additional advantages thereof, by aconsideration of the following detailed description of one or moreimplementations. Reference will be made to the appended sheets ofdrawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example aircraft in accordance with an example ofthe disclosure.

FIG. 2 illustrates an example horizontal stabilizer trim actuator inaccordance with an example of the disclosure.

FIGS. 3A-B illustrate an alternative directional and rate control valveconfiguration of a horizontal stabilizer trim actuator in accordancewith an example of the disclosure.

FIGS. 4A-B illustrate an alternative trim up solenoid operated valve andtrim down solenoid operated valve configuration of a horizontalstabilizer trim actuator in accordance with an example of thedisclosure.

FIGS. 5A-C illustrate alternative directional and rate controlconfigurations of a horizontal stabilizer trim actuator in accordancewith an example of the disclosure.

FIGS. 6A-E illustrate alternative shutoff valve configurations of ahorizontal stabilizer trim actuator in accordance with an example of thedisclosure.

FIG. 7 illustrates a flowchart detailing operation of a horizontalstabilizer trim actuator in accordance with an example of thedisclosure.

Examples of the disclosure and their advantages are best understood byreferring to the detailed description that follows. It should beappreciated that like reference numerals are used to identify likeelements illustrated in one or more of the figures.

DETAILED DESCRIPTION

Aircraft may include control surfaces such as, for example, horizontalcontrol surfaces located at an aft portion the aircraft. The horizontalcontrol surface may include one or more elevator control surfacescoupled to the horizontal control surface. The one or more elevatorcontrol surfaces may be used to, for example, change a pitch of theaircraft.

A Horizontal Stabilizer Trim Actuator (HSTA) may be used to move thecontrol surface (e.g., the horizontal control surface). The HSTA may,for example, change an angle of attack of the control surface or changea position of the control surface. The control surface may be moved to,for example, alleviate load on the one or more elevator control surface.In certain examples, un-commanded or unintended movement of the controlsurface may be undesirable. As such, a HSTA design minimizing the chanceof such un-commanded or unintended movement may be desirable.Additionally, it may be desirable to keep the design of the HSTA assimple as possible to improve reliability, decrease cost, and minimizeweight.

FIG. 1 illustrates an example aircraft in accordance with thedisclosure. The aircraft 100 of FIG. 1 may include a fuselage 170, wings172, horizontal stabilizers 174, aircraft engines 176, and a verticalstabilizer 178. The wings 172 s may include the movable wing components182A-G. The movable wing components 182A-G may be flaps, ailerons,flaperons, slats, and other movable components coupled to the wings 172.The horizontal stabilizers 174 may include the movable stabilizercomponents 184A-C. The movable stabilizer components 184A-C may beelevator or other movable components coupled to the horizontalstabilizers 174.

Additionally, the aircraft 100 may include a controller 108 and a flightdeck 110. The various components of the aircraft 100 may be linked withcommunications 112 to communicate commands and conditions detected. Theaircraft 100 described in FIG. 1 is exemplary and it is appreciated thatin other embodiments, the aircraft 100 may include less or additionalcomponents (e.g., no horizontal stabilizer or additional stabilizers).Additionally, concepts described herein may be extended to otheraircraft such as helicopters, Unmanned Aerial Vehicles, etc.

The flight deck 110 of the aircraft 100 may include controls that may bemanipulated by the pilot(s) of the aircraft 100 to provide instructionsfor the operation of the aircraft. For example, the flight deck 110 mayinclude a control or controls for determining the throttle position orwing and/or horizontal stabilizer configuration of the aircraft (e.g.,movement of the wings 172, horizontal stabilizers 174, movable wingcomponents 182A-G, and/or movable stabilizer components 184A-C). Theflight deck 110 may also include controls for determining aconfiguration of the horizontal stabilizer or other aerodynamic deviceof the aircraft 100 as well as the configuration of the verticalstabilizer.

The flight deck 110, the wings 172, the horizontal stabilizers 174, themovable wing components 182A-G, the movable stabilizer components184A-C, as well as other components, may be communicatively coupledthrough one or more communication channels 112. The communicationchannel 112 may, for example, be a digital communication channel such asa wired communication circuit or a wireless communications system or ananalog communication channel. The communication channel 112 may link thevarious components to the controller 108.

The controller 108 may include, for example, a single-core or multi-coreprocessor or microprocessor, a microcontroller, a logic device, a signalprocessing device, memory for storing executable instructions (e.g.,software, firmware, or other instructions), and/or any elements toperform any of the various operations described herein. In variousexamples, the controller 108 and/or its associated operations may beimplemented as a single device or multiple devices (e.g.,communicatively linked through analog, wired, or wireless connectionssuch as the communication channel 112) to collectively constitute thecontroller 108.

The controller 108 may include one or more memory components or devicesto store data and information. The memory may include volatile andnon-volatile memory. Examples of such memories include RAM (RandomAccess Memory), ROM (Read-Only Memory), EEPROM (Electrically-ErasableRead-Only Memory), flash memory, or other types of memory. In certainexamples, the controller 108 may be adapted to execute instructionsstored within the memory to perform various methods and processesdescribed herein, including implementation and execution of controlalgorithms responsive to sensor and/or operator (e.g., flight crew)inputs.

FIG. 2 illustrates an example horizontal stabilizer trim actuator (HSTA)in accordance with an example of the disclosure. The HSTA 200 shown inFIG. 2 includes a hydraulic shutoff apparatus 204 and a directional andrate control apparatus 214. Both the hydraulic shutoff apparatus 204 andthe directional and rate control apparatus 214 may include one or morecomponents.

The HSTA 200 may additionally include an inlet 202A and a filter 202B, ahydraulic motor 238, an output shaft 240, a hydraulic brake 242, a brakecontroller 244, a return check valve 246, anti-cavitation valves 248,and a return port 252.

The inlet 202A and the filter 202B are fluidically connected to thehydraulic shutoff apparatus 204 via the first hydraulic path 210. (Forthe purposes of this disclosure, when two components are “fluidicallyconnected” a fluid may flow from one component to the other. There maybe additional components between the two components that, in certainsituations, may shut off the flow of the fluid between the twocomponents. As long as the fluid may flow between the two components ina certain configuration, they are considered to be “fluidicallyconnected.”) As such, hydraulic fluid, which may be pressurized, mayflow from the inlet 202A, through the filter 202B, and through the firsthydraulic path 210 to the hydraulic shutoff apparatus 204.

In the example shown in FIG. 2, the hydraulic shutoff apparatus 204 mayinclude the shutoff SOV 208 and the shutoff spool 206. The shutoff SOV208 may be a normally closed 3-port 2-position solenoid operated valve.In certain examples, the solenoid operated valve may be operated by, forexample, the controller 108 (e.g., through an algorithm of thecontroller 108), from a pilot command, or through another operatingtechnique. The shutoff SOV 208 may control pilot pressure to the shutoffspool 206. The shutoff spool 206 may be a normally closed 3-port2-position pilot operated valve (e.g., operated by pilot pressure from,for example, the shutoff SOV 208). When the shutoff SOV 208 is energized(e.g., the solenoid is operated so that it is in the open position asopposed to the normally closed position) pilot pressure from thepressurized hydraulic fluid flowing from the first hydraulic path 210may energize the shutoff spool 206 (e.g., change the position of theshutoff spool 206 to an open position) such that the shutoff spool 206allows pressurized hydraulic fluid to flow from the first hydraulic path210 through the shutoff spool 206 to the directional and rate controlapparatus 214. Alternatively, when the shutoff SOV 208 is de-energized,the hydraulic fluid in the second hydraulic path 212 may be routed backto the return port 252.

The pressurized hydraulic fluid may then flow from the hydraulic shutoffapparatus 204 to the directional and rate control apparatus 214. Incertain examples, the directional and rate control apparatus 214 mayinclude a rate control SOV 216, a rate control spool 218, a control trimup SOV 220, a control trim down SOV 222, a directional control valve224, and a Linear Variable Differential Transformer (LVDT) 226. Otherexamples of the directional and rate control apparatus 214 may includeadditional, fewer, and/or different components.

The rate control SOV 216 may be a normally closed 3-port 2-positionsolenoid operated valve. The rate control SOV 216 may control pilotpressure to the rate control spool 218. The rate control spool 218 maybe a normally open 4-port 2-position pilot operated valve operated viapilot pressure from the rate control SOV 216. When the shutoff spool 206is energized, pressurized hydraulic fluid may flow into second hydraulicpath 212. From the second hydraulic path 212, the pressurized hydraulicfluid may flow to the rate control SOV 216. When the rate control spool216 is energized (e.g., switched from the closed position to an openposition), pilot pressure from the rate control SOV 216 may accordinglyenergize the rate control spool 218.

Pressurized hydraulic fluid from the second hydraulic path 212 may flowthrough the rate control spool 218. In a normal configuration (e.g.,when the rate control spool 218 is not energized), the rate controlspool 218 may be in a low flow resistance configuration (e.g., a highflow rate configuration). When the rate control spool 218 is energized,the rate control spool 218 may be in a high flow resistanceconfiguration (e.g., a low flow rate configuration) and provideadditional resistance to the flow of pressurized hydraulic fluid throughthe rate control spool 218. As such, operation of the rate control SOV216 may control the resistance of the rate control spool 218 to flow ofthe hydraulic fluid. In certain examples, the rate control spool 218 mayinclude two paths for pressurized hydraulic fluid to flow through.

Pressurized hydraulic fluid from the rate control spool 218 may flow tothe directional control valve 224. The directional control valve 224 maybe a 4-port 3-position control valve that is spring-centered andpressure-centered. The directional control valve 224 may bepressure-centered via pilot pressure from the control trim up SOV 220and the control trim down SOV 222. Pilot pressure from the control trimup SOV 220 may reach the directional control valve 224 via a fourthhydraulic path 232 and pilot pressure from the control trim down SOV 222may reach the directional control valve 224 via a fifth hydraulic path234. In examples where the rate control spool 218 includes two paths forpressurized hydraulic fluid to flow through, the directional controlvalve 224 may also receive the pressurized hydraulic fluid via twopaths.

The control trim up SOV 220 and the control trim down SOV 222 may bothbe normally open 3-port 2-position solenoid operated valves. The controltrim up SOV 220 and/or the control trim down SOV 222 may control pilotpressure from the respective control trim up/down SOV to the directionalcontrol valve 224. Energizing the control trim up SOV 220 and/or thecontrol trim down SOV 222 may change the configuration of the respectiveSOV to a closed position. In the closed position, pilot pressure may notbe present to the direction control valve 224. Additionally, pilotpressure restrictions 228 and 230 may additionally be coupled to thefourth hydraulic path 232 and the fifth hydraulic path 234. The pilotpressure restrictions 228 and 230 may control the flow and/or thepressure of hydraulic fluid through the fourth hydraulic path 232 andthe fifth hydraulic path 234 as an alternative technique of controllingthe configuration of the directional control valve 224. For example, theconfiguration of the directional control valve 224 may be controlled byrestricting none, one, or both of the flow of pressurized hydraulicfluid through the fourth hydraulic path 232 and/or the fifth hydraulicpath 234. The pilot pressure restrictions 228 and 230 may be controlledby the controller 108, by the pilot, fixed through mechanical means, orthrough another technique.

Referring back to the directional control valve 224, the currentdirectional control valve 224 may include 3 positions. When pilotpressure from both or neither of the control trim up 220 and the controltrim down 222 are present, the directional control valve 224 may be in afirst configuration that prevents flow through both of the paths thatthe pressurized hydraulic fluid flows through to the third hydraulicpath 236. In certain examples, the first configuration may be a centeredposition of the directional control valve 224. When pilot pressure fromonly one of the control trim up SOV 220 and the control trim down SOV222 is present, the directional control valve 224 may be in a secondconfiguration that allows flow of the pressurized hydraulic fluidlinearly through the directional control valve 224 or may be in a thirdconfiguration that crosses the flow of the hydraulic fluid through thedirectional control valve 224.

For example, the directional control valve 224 may include first andsecond inlets and first and second outlets. In the first configuration,no or minimal flow may be allowed through the directional control valve224. In the second configuration, hydraulic fluid entering the firstinlet may flow through to the first outlet and hydraulic fluid enteringthe second inlet may flow through to the second outlet. In the thirdconfiguration, hydraulic fluid entering the first inlet may flow throughto the second outlet and hydraulic fluid entering the second inlet mayflow through to the first outlet.

In certain examples, the position of the directional control valve 224may be monitored by the Linear Variable Displacement Transformer (LVDT)226. The LVDT 226 may determine and output data directed to the positionof the directional control valve 224 to the controller 108. Thecontroller 108 may then confirm, from the LVDT 226 output, that theposition of the directional control valve 224 is consistent with thatcommanded (e.g., via commands given to the solenoids of the control trimup SOV 220 and/or the control trim down SOV 222). Certain other examplesmay not include the LVDT 226. In such examples, the position of thedirectional control valve 226 may be determined from the commands issuedby the controller 108.

Pressurized hydraulic fluid exiting the directional control valve 224may flow into a third hydraulic path 236. The third hydraulic path 236may, for example, be fluidically connected to the hydraulic motor 238.The hydraulic motor 238 may be powered by the pressurized hydraulicfluid flowing from the directional control valve 224 into, for example,motor control ports of the hydraulic motor 238. In certain examples, thehydraulic motor 238 may be a fixed displacement bi-directional motorthat turns the output shaft 240. As such, when the directional controlvalve 224 is in the first configuration, no or minimal pressurizedhydraulic fluid may reach the hydraulic motor 238 and the hydraulicmotor 238 may be locked (e.g., may not be turning). When the directionalcontrol valve 224 is in the second configuration, the hydraulic motor238 may turn in a first direction and when the directional control valve224 is in the third configuration, the hydraulic motor 238 may turn in asecond direction.

The output shaft 240 may, in certain examples, be connected to a HSTAgearbox. The HSTA gearbox may control the displacement and/or rate ofchange of the horizontal stabilizers 174. The gearbox may be controlledby the controller 108, may be pilot controlled, may be controllerthrough mechanical means, may be a fixed gear ratio, or may becontrolled through another technique. In certain examples, there may bemultiple hydraulic motors 238 and/or multiple output shafts 240. In suchexamples, a speed-summing differential may be included to combine therotation of the multiple hydraulic motors 238 and/or the multiple outputshafts 240.

In certain examples, the anti-cavitation valves 248 may allow hydraulicfluid to enter the motor control ports if pressure within the thirdhydraulic path 236 drops below a return pressure (e.g., a pressure ofthe return line 250).

The hydraulic brake 242 may be a power-off brake (e.g., when pressurizedhydraulic fluid is not flowing into a port of the hydraulic brake 242,the brake may be set and may restrict rotation of the output shaft 240).In certain examples, the brake controller 244 may be a hydraulic brakesolenoid operated valve (SOV) though other examples may include othertypes of brake controllers, such as electronic controllers or othertypes of valves. The brake controller 244 may control pressure to thehydraulic brake 242. The brake controller 244 may be a normally closed3-port 2-position solenoid operated valve. When the brake controller 244is energized, pressurized hydraulic fluid may flow to the hydraulicbrake 242 and release the hydraulic brake 242. In certain examples, thepressurized hydraulic fluid may release the hydraulic brake 242 byovercoming a spring force holding the hydraulic brake 242 in a positionrestricting rotation of the output shaft 240. When the hydraulic brake242 is released, the hydraulic brake 242 may no longer or may minimallyrestrict movement of the output shaft 240. In certain examples, thebrake controller 244 and the hydraulic brake 242 may be replaced by anelectric power-off brake. In such examples, the electric power-off brakemay restrict movement of the output shaft 240 when engaged (e.g., whenan instruction is provided to the electric power-off brake from thecontroller 108).

In certain examples, a pressure switch and/or pressure transducer may beincluded between the brake controller 244 and the hydraulic brake 242.Additionally or alternatively, a LVDT may be coupled to the hydraulicbrake 242 (e.g., the brake piston of the hydraulic brake 242). Such anLVDT may provide information as to whether the hydraulic brake 242 isengaged.

Additionally, a return check valve 246 may be on the return line 250.The return check valve 246 may prevent system and return pressuretransients from reaching the hydraulic brake 242 (e.g., may preventmomentary pressures from disengaging the hydraulic brake 242). Incertain other examples, the return line 250 may include a hydraulicaccumulator alternative or in addition to the return check valve 246.The hydraulic accumulator may prevent cavitation of the hydraulic fluidwithin the hydraulic motor.

Various hydraulic paths of the HSTA 200 may be fluidically connected tothe return port 252. The return port 252 may be connected to a source ofpressurized hydraulic fluid. In certain examples, the return port 252may be fluidically connected to the same source of pressurized hydraulicfluid that provides fluid to the inlet 202. The return port 252 mayreceive excess hydraulic fluid pressure of the HSTA 200.

The HSTA 200 may provide for three independent techniques for shutdownwhen an un-commanded or unintended movement event is detected. Forexample, the shutoff SOV 208 may be de-energized (e.g., by thecontroller 108, the pilot, or another input). De-energizing the shutoffSOV 208 may block inlet pressure from the inlet 202 from reaching therest of the HSTA 200 and may connect the second hydraulic path 212 tothe return port 252. Additionally, the control trim up SOV 220 and thecontrol trim down SOV 222 may also be de-energized. De-energizing thecontrol trim up SOV 220 and the control trim down SOV 222 may cause thedirectional control valve 224 to transition to the first configurationand lock the hydraulic motor 238 in place. Also, the brake controller244 may be de-energized and cause the hydraulic brake 242 to engage torestrain movement of the output shaft 240. Restraining the movement ofthe output shaft 240 may prevent movement of any movable controlsurfaces (e.g., movable wing components 182A-G, movable stabilizercomponents 184A-C, and/or horizontal stabilizers 174) coupled to theHSTA 200.

FIGS. 3A-B illustrate an alternative directional and rate control valveconfiguration of a horizontal stabilizer trim actuator in accordancewith an example of the disclosure. FIG. 3A illustrates a directional andrate control component configuration 300A that includes the rate controlspool 218, the control trim up SOV 220, the control trim down SOV 222,the directional control valve 224, the LVDT 226, the fourth hydraulicpath 232, the fifth hydraulic path 234, and the pilot pressurerestrictions 228 and 230. The configuration shown in FIG. 3A may besimilar to that described in FIG. 2.

FIG. 3B may illustrate an alternative directional and rate controlcomponent configuration 300B. The alternative directional and ratecontrol component configuration 300B, may include a rate control spool318, a control trim up SOV 320, a control trim down SOV 322, adirectional control valve 324, a LVDT 326, fourth hydraulic path 332,fifth hydraulic path 334, and pilot pressure restrictions 328 and 330.

The alternative directional and rate control component configuration300B may be similar to the directional and rate control componentconfiguration 300A. However, in the alternative directional and ratecontrol component configuration 300B, pressurized hydraulic fluid fromthe second hydraulic path (not shown in FIG. 3B, but shown in FIG. 2)may flow to the directional control valve 324. The rate control spool318 may receive pressurized hydraulic fluid from the directional controlvalve 324. Pressurized hydraulic fluid may then flow from the ratecontrol spool 318 to the third hydraulic path 236 (not shown in FIG. 3B,but shown in FIG. 2).

FIGS. 4A-B illustrate an alternative trim up solenoid operated valve andtrim down solenoid operated valve configuration of a horizontalstabilizer trim actuator in accordance with an example of thedisclosure. FIG. 4A illustrates a control trim up and trim downconfiguration 400A that includes the control trim up SOV 220 and thecontrol trim down SOV 222. The configuration shown in FIG. 4A may besimilar to that described in FIG. 2.

FIG. 4B illustrates an alternative control trim up and trim downconfiguration 400B. The alternative control trim up and trim downconfiguration 400B includes a control trim up SOV 420 and a control trimdown SOV 422. The control trim up SOV 420 and the control trim down SOV422 may be normally closed SOVs. As such, when the control trim up SOV420 and the control trim down SOV 422 are un-commanded, the fourthhydraulic path 232 and the fifth hydraulic path 234 are fluidicallyconnected to the return line 250. The directional control valve (notshown in FIG. 4B, but shown in FIG. 2) may be spring-centered to itsfirst configuration. When one of the control trim up SOV 420 or thecontrol trim down SOV 422 is energized, pilot pressure may be ported tothe directional control valve 224. Such pressure may change the positionof the direction control valve 224 to a flow-through position.

FIGS. 5A-C illustrate alternative directional and rate controlconfigurations of a horizontal stabilizer trim actuator in accordancewith an example of the disclosure. FIG. 5A illustrates a directional andrate control configuration 500A that includes the rate control SOV 216,the rate control spool 218, the control trim up SOV 220, the controltrim down SOV 222, the directional control valve 224, the LVDT 226, thefourth hydraulic path 232, the fifth hydraulic path 234, and the pilotpressure restrictions 228 and 230. The configuration shown in FIG. 5Amay be similar to that described in FIG. 2.

FIG. 5B may illustrate an alternative directional and rate controlconfiguration 500B. The alternative directional and rate controlconfiguration 500B may include an electro-hydraulic servo valve 524-1and a LVDT 526. The electro-hydraulic servo valve 524-1 may be a 4-port3-position electronically controlled valve. The electro-hydraulic servovalve 524-1 may be controlled by an external source such as thecontroller 108, input from the pilot, or from another technique. TheLVDT 526 may monitor the position of the electro-hydraulic servo valve524-1.

FIG. 5C may illustrate another alternative directional and rate controlconfiguration 500C. The directional and rate control configuration 500Cmay include a direct drive valve 524-2 and the LVDT 526. The directdrive valve 524-2 may be a 4-port 3-position linear or rotary directdrive valve. The LVDT 526 may monitor the position of the direct drivevalve 524-2.

FIGS. 6A-E illustrate alternative shutoff valve configurations of ahorizontal stabilizer trim actuator in accordance with an example of thedisclosure. FIG. 6A illustrates a shutoff valve configuration 600A thatincludes the shutoff SOV 208 and the shutoff spool 206. Theconfiguration shown in FIG. 6A may be similar to that described in FIG.2.

FIGS. 6B-E may illustrate alternative shutoff valve configurations600B-E. The shutoff valve configuration 600B may include a motoroperated 3-port 2-position shutoff valve 606-1. The shutoff valveconfiguration 600C may include a solenoid operated 3-port 2-positionshutoff valve 606-2. The shutoff valve configuration 600D may replacethe 3-port 2-position shutoff spool 206 of configuration 600A with apilot operated 2-port 2-position shutoff valve. The shutoff valveconfiguration 600E may include a motor operated 2-port 2-positionshutoff valve.

FIG. 7 illustrates a flowchart detailing operation of a horizontalstabilizer trim actuator in accordance with an example of thedisclosure. In block 702, pressurized hydraulic fluid may flow throughthe inlet 202 and the filter 210. In block 704, instructions from thecontroller 108 and/or the pilot may be provided to the shutoffapparatus. The controller 108 and/or the pilot may, for example, provideinstructions to energize the solenoid of the shutoff SOV 208. In block706, the instructions may be received and, if the solenoid of theshutoff SOV 208 is to be energized, the shutoff apparatus is opened andthe process may proceed to block 710. If the solenoid of the shutoff SOV208 is de-energized, the shutoff apparatus is not opened, and theprocess may proceed to block 708 and connect pressurized hydraulic fluidto the return port 252 and, thus, de-pressurize the hydraulic fluid.

In block 710, pressurized hydraulic fluid may flow to the directionaland rate control apparatus. In block 712, the flow rate through the ratecontrol spool 218 may be controlled. The controller 108 and/or the pilotmay control the flow rate through the rate control spool 218 by, forexample, energizing or de-energizing the rate control SOV 216 to controlthe restriction of the rate control spool 218 to the flow of pressurizedhydraulic fluid.

In block 714, the control trim up SOV 220 and/or the control trim downSOV 222 may receive instructions from the controller 108 and/or thepilot. The instructions may operate the solenoid of the control trim upSOV 220 and/or the control trim down SOV 222 and/or may operate one orboth of the pilot pressure restrictions 228 and/or 230. If, from block714, the pilot pressure from the control trim up SOV 220 and the controltrim down SOV 222 are in equal block 716, the process may switch thedirectional control valve 224 to a blocked position (e.g., the firstconfiguration described in FIG. 2) in block 718. Otherwise, the processmay proceed to block 720 and switch the directional control valve 224 toa flow-through position (e.g., a position where pressurized hydraulicfluid may flow through the directional control valve 224 such as thesecond or third configuration described in FIG. 2).

The flow of pressurized hydraulic fluid through the directional controlvalve 224 may power the hydraulic motor 238 in block 722. Additionally,in block 724, instructions may be received to release the hydraulicbrake 242. If instructions are received for releasing the hydraulicbrake 242, the hydraulic brake SOV 244 may be opened and may release thehydraulic brake 242 in block 726. The output shaft 240 may then beturned in block 728.

Examples described above illustrate but do not limit the invention. Itshould also be understood that numerous modifications and variations arepossible in accordance with the principles of the present invention.Accordingly, the scope of the invention is defined only by the followingclaims.

What is claimed is:
 1. A system comprising: a hydraulic inlet configuredto receive pressurized hydraulic fluid; a first hydraulic pathfluidically connected to the hydraulic inlet; a second hydraulic path; ahydraulic shutoff apparatus fluidically connected to the first hydraulicpath and the second hydraulic path and configured to be switched betweena plurality of hydraulic positions wherein at least one of the hydraulicpositions allows for the pressurized hydraulic fluid to flow from thefirst hydraulic path through the hydraulic shutoff apparatus to thesecond hydraulic path; a directional and rate control apparatus; a thirdhydraulic path fluidically connected to the directional and rate controlapparatus; and a hydraulic motor fluidically connected to thedirectional and rate control apparatus via the third hydraulic path,wherein: the directional and rate control apparatus is configured to beswitched between a plurality of directional control positions wherein atleast one of the directional control positions allows for thepressurized hydraulic fluid to flow from the second hydraulic paththrough the directional and rate control apparatus to the hydraulicmotor, and the hydraulic motor is configured to turn an output shaft toactuate a control surface of a vehicle responsive to receiving thepressurized hydraulic fluid from the directional and rate controlapparatus and configured to be locked responsive to not receiving thepressurized hydraulic fluid from the directional and rate controlapparatus.
 2. The system of claim 1, further comprising: a brakecontroller fluidically connected to the hydraulic shutoff apparatus viathe second hydraulic path, wherein the brake controller is configured toallow flow of the pressurized hydraulic fluid in an open position andconfigured to prevent flow of the pressurized hydraulic fluid in aclosed position; and a hydraulic brake configured to restrict movementof the hydraulic motor and/or the output shaft responsive to notreceiving the pressurized hydraulic fluid from the brake controller. 3.The system of claim 2, wherein the brake controller is a hydraulic brakesolenoid operated valve (SOV) comprising a three port two position SOV.4. The system of claim 1, wherein the hydraulic shutoff apparatuscomprises: a shutoff SOV fluidically connected to the first hydraulicpath, wherein the shutoff SOV is a three port two position SOVconfigured to allow flow of the pressurized hydraulic fluid in an openposition and configured to prevent flow of the pressurized hydraulicfluid in a closed position; and a shutoff spool fluidically connected tothe first hydraulic path, wherein the shutoff spool is a three port twoposition pilot operated valve configured to, responsive to the shutoffSOV allowing flow of the pressurized hydraulic fluid, allow flow of thepressurized hydraulic fluid from the first hydraulic path to thedirectional and rate control apparatus.
 5. The system of claim 1,wherein directional and rate control apparatus comprises a directionalcontrol valve and a rate apparatus comprising: a rate control SOVfluidically connected to the second hydraulic path, wherein the ratecontrol SOV is a three port two position SOV configured to allow flow ofthe pressurized hydraulic fluid to a rate control spool in an openposition and configured to prevent flow of the pressurized hydraulicfluid in a closed position; and the rate control spool, wherein the ratecontrol spool is a four port two position pilot operated valveconfigured to, responsive to the rate control SOV allowing flow of thepressurized hydraulic fluid, further restrict flow of hydraulic fluidthrough the rate control spool.
 6. The system of claim 5, wherein therate control spool is fluidically connected to the second hydraulic pathand configured to allow flow of the pressurized hydraulic fluid from thesecond hydraulic path through the rate control spool to the directionalcontrol valve and the directional control valve is fluidically connectedto the hydraulic motor.
 7. The system of claim 5, wherein thedirectional control valve is fluidically connected to the secondhydraulic path, the at least one of the directional control positions isconfigured to allow flow of the pressurized hydraulic fluid from thesecond hydraulic path through the directional control valve to the ratecontrol spool, and the rate control spool is fluidically connected tothe hydraulic motor.
 8. The system of claim 1, further comprising: afourth hydraulic path; a fifth hydraulic path, wherein the directionaland rate control apparatus comprises a directional control valve and apressure centered apparatus fluidically connected to the fourthhydraulic path and the fifth hydraulic path and configured to switchbetween the plurality of directional control positions responsive to theflow of the pressurized hydraulic fluid from the fourth hydraulic pathand the fifth hydraulic path; a control trim up SOV fluidicallyconnected to the second hydraulic path and the fourth hydraulic path,wherein the control trim up SOV is a three port two position SOVconfigured to allow flow of the pressurized hydraulic fluid to thefourth hydraulic path in an open position and configured to prevent flowof the pressurized hydraulic fluid in a closed position; and a controltrim down SOV fluidically connected to the second hydraulic path and thefifth hydraulic path, wherein the control trim down SOV is a three porttwo position SOV configured to allow flow of the pressurized hydraulicfluid to the fifth hydraulic path in an open position and configured toprevent flow of the pressurized hydraulic fluid in a closed position. 9.The system of claim 8, wherein the directional control valve is a fourport valve and is configured to be switched between at least threepositions comprising a first position configured to prevent flow of thepressurized hydraulic fluid through the directional control valve, asecond position configured to allow for the pressurized hydraulic fluidto flow through the directional control valve to the hydraulic motor ina first manner, and a third position configured to allow for thepressurized hydraulic fluid to flow through the directional controlvalve to the hydraulic motor in a second manner.
 10. The system of claim9, wherein the directional control valve is configured to: be in thefirst position responsive to substantially equal hydraulic pressurewithin the fourth hydraulic path and the fifth hydraulic path; be in thesecond position responsive to hydraulic pressure that is substantiallygreater within the fourth hydraulic path than within the fifth hydraulicpath; and be in the third position responsive to hydraulic pressure thatis substantially greater within the fifth hydraulic path than within thefourth hydraulic path.
 11. The system of claim 10, further comprising: afirst pilot operated restriction coupled to the fourth hydraulic pathand configured to restrict flow of the pressurized hydraulic fluidthrough the fourth hydraulic path; and a second pilot operatedrestriction coupled to the fifth hydraulic path and configured torestrict flow of the pressurized hydraulic fluid through the fifthhydraulic path.
 12. The system of claim 8, wherein the control trim upSOV is configured to be normally in the open position and the controltrim down SOV is configured to be normally in the open position.
 13. Thesystem of claim 8, wherein the control trim up SOV is configured to benormally in the closed position and the control trim down SOV isconfigured to be normally in the closed position.
 14. The system ofclaim 1, wherein the directional and rate control apparatus isconfigured to be switched between the plurality of positions by anelectro-hydraulic servo valve and/or a direct drive valve and thedirectional and rate control apparatus is fluidically connected to thesecond hydraulic path.
 15. The system of claim 1, wherein the hydraulicshutoff apparatus comprises: a shutoff SOV fluidically connected to thefirst hydraulic path, wherein the shutoff SOV is a three port twoposition SOV configured to allow flow of the pressurized hydraulic fluidin an open position and configured to prevent flow of the pressurizedhydraulic fluid in a closed position; and a shutoff spool fluidicallyconnected to the first hydraulic path, wherein the shutoff spool is atwo port two position pilot operated valve configured to, responsive tothe shutoff SOV allowing flow of the pressurized hydraulic fluid, allowflow of the pressurized hydraulic fluid from the first hydraulic path tothe directional and rate control apparatus.
 16. The system of claim 1,wherein the hydraulic shutoff apparatus comprises one of: a shutoffvalve fluidically connected to the first hydraulic path, wherein theshutoff valve is a three port two position motor operated valveconfigured to allow flow of the pressurized hydraulic fluid in an openposition and configured to prevent flow of the pressurized hydraulicfluid in a closed position; a shutoff valve fluidically connected to thefirst hydraulic path, wherein the shutoff valve is a two port twoposition motor operated valve configured to allow flow of thepressurized hydraulic fluid in an open position and configured toprevent flow of the pressurized hydraulic fluid in a closed position; ora shutoff valve fluidically connected to the first hydraulic path,wherein the shutoff valve is a two port two position solenoid operatedvalve configured to allow flow of the pressurized hydraulic fluid in anopen position and configured to prevent flow of the pressurizedhydraulic fluid in a closed position.
 17. The system of claim 1, furthercomprising an inlet filter disposed between the hydraulic inlet and thefirst hydraulic path.
 18. The system of claim 1, further comprising areturn port fluidically connected to the directional and rate controlapparatus.
 19. The system of claim 1, wherein the directional and ratecontrol apparatus further comprises a linear variable differentialtransformer configured to monitor the position of the directionalcontrol valve
 20. The system of claim 1, further comprising: an electricbrake configured to restrict movement of the hydraulic motor and/or theoutput shaft responsive receiving an engagement instruction.
 21. Anaircraft comprising the apparatus of claim 1, wherein the vehicle is theaircraft and the aircraft comprises: a fuselage; and the control surfacecoupled to the fuselage.
 22. A method comprising: receiving pressurizedhydraulic fluid; flowing the pressurized hydraulic fluid into ahydraulic shutoff apparatus; switching, responsive to the flow of thepressurized hydraulic fluid into the hydraulic shutoff apparatus, thehydraulic shutoff apparatus to a first hydraulic position; flowing thepressurized hydraulic fluid into a directional and rate controlapparatus; switching, responsive to the flow of the pressurizedhydraulic fluid into the directional and rate control apparatus, adirectional control valve of the directional and rate control apparatusto a first directional control position; monitoring the position of thedirectional control valve; actuating, responsive to the flow of thepressurized hydraulic fluid into the hydraulic motor, the hydraulicmotor; turning an output shaft of the hydraulic motor; and actuating acontrol surface.
 23. The method of claim 22, wherein switching thehydraulic shutoff apparatus to a first hydraulic position comprises:switching a shutoff solenoid operated valve (SOV) to an open position toallow flow of the pressurized hydraulic fluid to a shutoff spool; andswitching the shutoff spool, responsive to the flow of the pressurizedhydraulic fluid to the shutoff spool, to flow the pressurized hydraulicfluid into the directional and rate control apparatus and a brakecontroller.
 24. The method of claim 22, wherein switching thedirectional control valve of the directional and rate control apparatusto a first directional control position comprises: flowing pressurizedhydraulic fluid through at least one of a fourth hydraulic path via acontrol trim up SOV and/or a fifth hydraulic path via a control trimdown SOV such that hydraulic pressure through the fourth hydraulic pathand the fifth hydraulic path are substantially different; and switchingthe directional control valve to a flow-through configuration responsiveto the substantially different hydraulic pressure in the fourthhydraulic path and the fifth hydraulic path to flow the pressurizedhydraulic fluid to the hydraulic motor.
 25. The method of claim 24,wherein switching the directional control valve further comprisesrestricting flow of the pressurized hydraulic fluid through a trim upSOV or a trim down SOV.
 26. The method of claim 22, further comprising:switching a rate control SOV to an open position to allow flow of thepressurized hydraulic fluid to a rate control spool; and restrictingflow of hydraulic fluid through the rate control spool responsive to therate control SOV allowing flow of the pressurized hydraulic fluid to therate control spool.
 27. The method of claim 22, wherein the directionalcontrol valve is switched between the plurality of positions by anelectro-hydraulic servo valve and/or a direct drive valve and thedirectional control valve is fluidically connected to the secondhydraulic path.
 28. The method of claim 22, further comprising:switching a brake controller to an open position to allow flow of thepressurized hydraulic fluid to a hydraulic brake; and releasing thehydraulic brake configured responsive to the flow of the pressurizedhydraulic fluid from the brake controller to the hydraulic brake.